A variant of fasting is intermittent fasting (Latin “intermittere”: to interrupt; synonyms: Intermittent fasting; “every other day diet” (EOD; every other day diet); “alternate day fasting” (ADF)). This involves alternating periods of “normal” food intake with periods of fasting or significantly restricted food intake in a defined rhythm. The number of fasting periods or their duration can be determined individually.
Principles and goals
Researchers believe that the dietary pattern of intermittent fasting is more similar to that of humans before the advent of agriculture and animal husbandry than our current eating habits, which, among other things, lead to obesity in one in two people. For our ancestors, in fact, days without food intake were not uncommon. Studies show that regular fasting days are associated with a longer life expectancy and health-promoting effects. In animal experiments, a life-extending effect of up to 40% was observed. Furthermore, the risk of age-related diseases such as diabetes mellitus type 2, cardiovascular (affecting the cardiovascular system) diseases and tumor diseases decreased by 40 to 50%. The organism is relieved by regular fasting days and seems to become more resistant.
Principle of action
The beneficial effects of intermittent fasting are attributed to the reduction of energy intake and, consequently, are comparable to those of caloric restriction (see the topic “Caloric Restriction”), which has been shown to result in physiological and metabolic changes. Calorie restriction lowers fasting glucose (fasting blood sugar) and blood pressure, and reduces DNA damage. Likewise, there is a decrease in insulin levels and a decrease in tumor necrosis factor-alpha. One reason for the lower accumulation of oxidation products is primarily the lower radical formation rate, which is due to a lower metabolism and lower oxygen consumption. Furthermore, increased apoptosis (programmed cell death) of premalignant precursor cells (malignant precursor cells) and increased autophagy (see below) can be achieved, for example, by 12- to 14-hour food abstinence (deprivation of food). The start of programmed cell death is the release of the protein cytochrome c from the mitochondria into the cell interior. For this purpose, the otherwise dense membrane of the mitochondria becomes permeable. After this step, the initiation of apoptosis is irreversible (irreversible) and the cell is degraded. Autophagy serves cellular quality control (“recycling program”). For example, misfolded proteins or damaged cell organelles that could impair the functionality of a cell are eliminated and self-digested (autophagy = “eating oneself”). This process takes place intracellularly. A lack of energy or nutrients (amino acids), leads to a stimulation or increase of autophagy. A recent study found that carbohydrate deficiency also increases autophagy. Both an energy deficiency and a carbohydrate deficiency initiate the sending of a signal via the so-called WIPI4 protein (WIPI: WD-repeat protein interacting with phosphoinositides). This regulates the extent of degradation by autophagy. To date, four WIPI proteins (WIPI1-4) are known to be involved in the regulation of autophagy. Dysregulated or decreased autophagy is present in many age-related diseases such as type 2 diabetes mellitus, tumor diseases, or neurodegenerative diseases. Caloric restriction is also associated with a reduction in mitotic velocity and increased DNA repair. In summary, reduction of energy intake or deficiency of the macronutrients amino acids and carbohydrates has the following effects at the cellular level:
- Reduced mitochondrial oxidative stress.
- Reduced sirtuin-mediated aging processes (sirtuin-1 = enzyme in mammals associated with aging processes).
- Increased gene expression (“biosynthesis”) cell-protective stress proteins.
- Increased autophagy (synonym: autophagocytosis; “self-consuming”) as well as apoptosis (programmed cell death).
Implementation
There are several variations of intermittent fasting. So you can choose one or two days of fasting per week, or daily periods of fasting.Ideally, the phase of food abstinence should last at least 16 hours.A 24-hour rhythm is often chosen, that is, a period of 24 hours of fasting is followed by a period of 24 hours of normal food intake.Other following rhythms are possible within the framework of daily fasting periods:
- 16:8 rhythm – a 16-hour fasting period is followed by an 8-hour phase of food intake.
- 18:6 rhythm – an 18-hour fasting period is followed by a 6-hour period of food intake.
- 20:4 rhythm – a 20-hour fasting period is followed by a 4-hour period of food intake.
- 36:12 rhythm – every other day is fasted
During the fasting period, solid food is avoided. Fluid intake is in the form of mineral or tap water and unsweetened teas or coffee.In the phase of food intake can be limited or at will (“ad libitum”). The diet should be full and varied, and meals should not be hypercaloric (increased caloric intake in excess of requirements). If energy intake is reduced, for example because the person wants to reduce weight, special attention should be paid to adequate and high-quality intake of macro- and micronutrients. Example of the sequence of an 18:6 rhythm:
- Around 11:00: first meal of the day.
- Around 16.00: last meal of the day
- The fasting period thus lasts from about 17:00 until the next day at 11:00
The more intense fasting, the faster the desired goals, such as weight loss, are achieved. After reaching the goal, the fasting days can be inserted again at greater intervals. The most intensive rhythm is the 24-hour rhythm. Researchers recommend interval fasting every three to six months for overall health improvement.
Nutritional assessment
Unlike total fasting, such as therapeutic fasting, the body receives food fairly regularly and does not also have to rely on its own proteins for energy, which would result in a loss of muscle mass.Side effects, such as hypotension (low blood pressure), fatigue, decreased ability to concentrate, increased sensation of cold, which occur with total fasting, are not to be expected with intermittent fasting. Intermittent fasting is associated with risk reduction for the following diseases:
- Renal disease – maintenance of glomerular filtration rate (GFR) as well as renal plasma flow (RPF) in the elderly.
- Degenerative diseases of the nervous system
- Diabetes mellitus – animals fed by the method of intermittent fasting had significantly lower levels of glucose and insulin
- Cardiovascular diseases
- Apoplexy (stroke)
- Tumor diseases (cancers) – by reducing metabolic and hormonal risk factors.
Indications (areas of application)
- Diabetes mellitus – slowing of progression (progression) of diabetic nephropathy (secondary disease of diabetes mellitus in which the kidneys are damaged by microangiopathy (vascular changes affecting the small vessels)) and improvement of diabetic metabolic status.
- Hypertension (high blood pressure)
- Alzheimer’s disease – preservation or improvement of cognitive abilities.
- Multiple sclerosis – neuroprotective effects.
- Secondary prevention of tumor diseases (hepatocellular carcinoma (liver cancer), breast carcinoma (breast cancer)) – prolonged survival; reduced tumor growth.
- Tertiary prevention of breast cancer – by prolonged food abstinence: in one study, the likelihood of recurrence was increased by 36% with a shorter duration of food abstinence (of less than 13 hours during sleep) compared with a longer duration of fasting (24 hours from the first to the last meal) (hazard ratio: 1.36; 95% confidence interval between 1.05 and 1.76; p = 0.02). In the study, 80% of women with an average age of 52 years were in the early stages (I and II) of breast cancer.
- Micronutrient deficiency (vital substances) – see therapy with micronutrients.
- Overweight – Intermittent fasting is very good for sustainable weight loss. People find it easier to do without food for a few days and then eat “normally” again than to permanently count calories.
The first human studies were able to confirm in tumor patients the positive effects of fasting on the effects of chemotherapy, which had already been established in animal studies. The side effects of cytostatic therapy could be significantly reduced by fasting for three to 5 days with 400 to 500 calories per day before starting chemotherapy. Food restriction causes healthy cells to downregulate proliferative signaling pathways, allowing the saved energy to be used for cell maintenance and repair processes.
Contraindications
- Pregnancy and lactation
People with health problems should get a medical examination before starting intermittent fasting.
Conclusion
Intermittent fasting is very easy to implement in everyday life, because it is rich in variants and therefore individually adaptable.The positive effects of intermittent fasting are so far largely proven by animal studies. The extent to which these can be transferred to humans is the subject of current studies. Random studies on fasting humans already indicate that the described healing and preventive effects of fasting can also be observed in humans.
